WO2005083828A1

WO2005083828A1 - Nonaqueous electrolyte and nonaqueous electrolyte secondary battery

Info

Publication number: WO2005083828A1
Application number: PCT/JP2005/003677
Authority: WO
Inventors: Takashi Hayashi; Akio Hiwara; Akira Yajima; Shusuke Inada; Sayaka Fukui
Original assignee: Kabushiki Kaisha Toshiba; Mitsui Chemicals, Inc.
Priority date: 2004-02-27
Filing date: 2005-02-25
Publication date: 2005-09-09
Also published as: TW200532963A; CN1965437A; JP2005243490A; JP4580662B2; KR20060116852A; TWI265651B; KR100811917B1

Abstract

Disclosed is a nonaqueous electrolyte secondary battery wherein safety during overcharge is further improved. Specifically disclosed is a nonaqueous electrolyte secondary battery having such a structure that an electrode group (3) including a positive electrode (10), a negative electrode (11) and a separator (12) is arranged within a space hermetically sealed by a container body (2) and a covering plate (4), and a nonaqueous electrolyte is injected into the electrode group(3). In this secondary battery, it is used a nonaqueous electrolyte obtained by dissolving an electrolyte in a nonaqueous solvent which contains halogenated benzenes while having the aminated benzene content, as impurities, of less than 100 ppm.

Description

Specification

Non-aqueous electrolyte and non-aqueous electrolyte secondary battery

【Technical field】

The present invention relates to a non-aqueous electrolyte and a non-aqueous electrolyte secondary battery.

[Background Art]

In recent years, in order to reduce the size and weight of electronic devices such as mobile communication devices, notebook computers, palmtop computers, integrated video cameras, portable CD (MD) players, and cordless telephones, In particular, small and large-capacity batteries are required as a power source.

Batteries that are widely used as power sources for these electronic devices include primary batteries such as lithium-manganese batteries, and secondary batteries such as nickel-cadmium batteries and lead-acid batteries. Among these, non-aqueous electrolyte secondary batteries using lithium composite oxide for the positive electrode and carbonaceous material capable of occluding and releasing lithium ions for the negative electrode are small, lightweight, have high cell voltage, and have high energy density. Is attracting attention.

By the way, with the recent increase in energy density of batteries, it is becoming more and more difficult to maintain safety during overcharge and to prevent a significant rise in battery temperature and, consequently, thermal runaway of batteries. There are many prior literatures and patent documents related to safety at the time of overcharging, which improve the safety of the battery by improving the structure of the battery, and improve safety by adding an overcharge additive to the non-aqueous electrolyte. The main thing is to plan. In particular, various proposals have been made when adding an overcharge additive to a non-aqueous electrolyte, since there are few structural restrictions.

Benzenes having a methyl group and a methoxy group, such as 4-methoxytoluene, 2,6-methoxytoluene, and 3,4,5-trimethoxytoluene, are used as overcharge additives. A redox shuttle having a reduction potential of about 4.8 to 4.9 V is known (for example, see Japanese Patent Application Laid-Open No. Hei 7-32014).

Furthermore, benzenes having an alkyl group and a halogen atom, such as 2-chloro-p-xylene and 4-bromo_m-xylene, are known (for example, see Japanese Patent Application Laid-Open No. 9-50822). Gazette). Examples of Japanese Patent Application Laid-Open No. 9-50882 It is described that the heat generation starting voltage of a battery obtained by adding such benzenes to a non-aqueous electrolyte is in the range of 4.45 to 4.75 V.

Further, benzenes substituted with a halogen atom and a alkoxy group, such as 1,2-dimethoxybenzene and 1,2-dimethoxy-14-phenolenobenzene, are known (for example, see Japanese Patent Application Laid-Open No. 1 56 243).

The benzenes described in JP-A-7-3026-14, JP-A-9-50822, and JP-A-2000-156243 are all available when the non-aqueous electrolyte battery is fully charged. It has a reversible oxidation-reduction potential at a more noble battery potential than the positive electrode potential. By adding these to the non-aqueous electrolyte, the oxidative decomposition reaction of the non-aqueous solvent that occurs during an overcharged state is promoted. The overcharge current is cut off using the heat generated by the oxidative decomposition reaction.

Further, it has been proposed that benzenes having a fluorine atom and a hydrocarbon group having 1 to 10 carbon atoms be contained in a non-aqueous electrolyte solution (for example, see Japanese Patent Application Laid-Open No. H11-329496). ). Japanese Patent Application Laid-Open No. 11-3294996 describes that the benzenes suppress the exothermic reaction by suppressing the reaction rate between the positive electrode and the non-aqueous electrolyte.

Furthermore, a lithium salt as the electrolyte, ethylene carbonate 20-60 volume ^_0/0, dialkyl carbonate 20-70 volume ^_0/0 and fluorinated toluene (2 Fuzoreoro Tonoreen, 3 Funoreoro Tonoreen, 4 Funore silo Tonoreen An organic electrolyte containing 5 to 30% by volume of an organic solvent has been proposed (see, for example, JP-A-2001-256996). According to Japanese Patent Application Laid-Open No. 2001-256996, the use of the organic electrolyte suppresses an increase in the internal pressure of the battery when left at a high temperature for a long time, thereby preventing the battery, particularly the vent portion, from being damaged. The stability of the battery is improved.

As described above, Japanese Patent Application Laid-Open No. Hei 7-302614, Japanese Patent Application Laid-Open No. 9-508222, Japanese Patent Laid-Open No. 2000-156423, Japanese Patent Application Laid-Open No. 11-329496, Japanese Patent Application Laid-Open No. 2001-256996 describes that a benzene having a methyl group, a methoxy group, a halogen atom or the like on a benzene ring is added to a non-aqueous electrolyte (or a non-aqueous electrolyte). It is described that the safety and stability of the battery are improved. But However, there is a strong need for batteries that have improved safety during overcharge.

Note that Japanese Patent Application Laid-Open Nos. Hei 7-3202614, Hei 9-51082, Japanese Patent Laid-Open No. 2000-1563243, Hei 1-132 Neither the publication No. 9496 nor the publication of Japanese Patent Application Laid-Open No. 2001-256696 describes a description of impurity components contained in the non-aqueous electrolyte.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a non-aqueous electrolyte and a non-aqueous electrolyte secondary battery with remarkably high safety during overcharge.

In the course of research for solving the above-mentioned problems, the present inventor has proposed a non-charge additive containing a benzene having a methyl group and a halogen atom as an overcharge additive that has an effect of preventing further progress of charging of a battery. In water electrolytes, it has been found that aminated benzenes, which are raw materials for producing the benzenes, exist as impurities and adversely affect the safety of the battery during overcharge.

As a result of further research based on these findings, they found that the content of aminated benzenes in the nonaqueous electrolyte had a particularly large effect on the safety of nonaqueous electrolyte secondary batteries during overcharge. The present invention has been completed.

The present invention provides a non-aqueous electrolyte containing a non-aqueous solvent and an electrolyte, wherein the non-aqueous solvent contains halogenated benzenes and the content of aminated benzenes contained as impurities in the non-aqueous solvent is 100 ppm. A non-aqueous electrolyte characterized by being less than

Further, the non-aqueous electrolyte of the present invention is characterized in that the non-aqueous solvent contains carbonates and / or γ-petit mouth ratatones together with halogenated benzenes.

Further, the non-aqueous electrolyte of the present invention is characterized in that the halogenated benzene is at least one selected from halogenated toluene and halogenated xylene having one or more chlorine atoms and / or fluorine atoms. Features.

Further, in the non-aqueous electrolyte of the present invention, the above-mentioned halogenated benzenes are at least selected from ο-chlorotoluene, ρ-chlorotoluene and ο-funoleotoluene. It is also characterized by one kind.

Further, the non-aqueous electrolyte of the present invention is characterized in that the aminated benzene is at least one selected from aminated toluene and xamino xylene. Further, the nonaqueous electrolyte of the present invention is characterized in that the aminated benzene is at least one selected from 2-aminotoluene, 4-aminotoluene and aminoxylene.

Further, the present invention is a nonaqueous electrolyte secondary battery including a positive electrode, a negative electrode, and any one of the above nonaqueous electrolytes.

[Brief description of the drawings]

The objects, features and advantages of the present invention will become more apparent from the following detailed description and drawings.

FIG. 1 is a perspective view schematically showing a configuration of a nonaqueous electrolyte secondary battery according to a first embodiment of the present invention.

FIG. 2 is a partial cross-sectional view taken along the line II-II of FIG.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

(Non-aqueous electrolyte)

The nonaqueous electrolyte of the present invention contains a nonaqueous solvent and an electrolyte, the nonaqueous solvent contains halogenated benzenes and aminated benzenes as impurities, and the content of the aminated benzenes in the nonaqueous solvent is 1%. It is characterized by being less than 0 ppm.

In the non-aqueous electrolyte of the present invention, the non-aqueous solvent preferably contains carbonates and / or γ-butyrolactone together with halogenated benzenes. Carbonates and γ-petit mouth ratatones can improve the ionic conductivity and redox stability of the nonaqueous electrolyte.

Since the non-aqueous electrolyte of the present invention has relatively low reactivity with the positive electrode during overcharge, the reaction between the positive electrode and the non-aqueous electrolyte immediately ends after the current is cut off. Therefore, it is possible to prevent the nonaqueous electrolyte secondary battery from causing thermal runaway.

In the non-aqueous electrolyte of the present invention, the halogenated benzenes contained in the non-aqueous solvent Known ones can be used, and among them, halogenated benzenes having one or two or more halogen atoms or methyl groups as substituents on a benzene ring are preferable. Among such halogenated benzenes, halogenated toluene, halogenated xylene and the like are preferable. As the halogen atom, chlorine and fluorine are preferred. Iodine and bromine are not preferred because they are easily decomposed in batteries. Specific examples of halogenated tonolenes include o-chlorotoluene, _m -chlorotonolene, p-chlorotonolene, o-funorelotone, m_hustreolotonolene, 2, ,, 3-dichlorotonolene and 2,4-dichlorotonolene. 2,5-Dichlorotonolene, 2,6-Dichlorotonolene, 3,4-Dichlorotonolene, 2,3-Diphnolelotonelene, 2,4-Diphnoletone Tonolene, 2,5-Diphnoletone Toluene, 2, 6-1 Halogenated toluene, in which one or two or more halogen atoms are substituted on the benzene ring by one or two or more, such as diphnolelothenolene, 2-chloro mouth_4 -phneolelothonolene, 2-chloro-6-fluorotoluene No.

Specific examples of halogenated xylene include 2-chloro-p-xylene, 2-chloro: m-xylene, 3-chloro-one o-xylene, 4-chloro-one o-xylene, 2,5-dichloro-p -Xylene, 2-funoleollow p-xylene, 2-funoleol mouth _ m-xylene, 3-funolene low o-xylene, 4-funolene low o-xylene, 2,5-difluoro: p-xylene, etc. on the benzene ring And halogenated xylene in which one or more halogen atoms are substituted with one or more halogen atoms.

One kind of the benzenes can be used alone or two or more kinds can be used in combination. Although the content of the lipophilic benzenes in the non-aqueous solvent is not particularly limited, it is preferably 0.1 to 15% by weight, more preferably 0.5 to 10% by weight, and particularly preferably 0.5 to 10% by weight of the total amount of the non-aqueous solvent. Is 1 to 8% by weight.

Known carbonates may be used together with the halogenated benzenes, and examples thereof include cyclic carbonates and chain carbonates. As the cyclic carbonate, ethylene carbonate, propylene carbonate and the like are preferably used. As the chain carbonate, dimethyl carbonate, ethyl methyl carbonate, getyl carbonate and the like are preferably used. Can be

One type of carbonate can be used alone or two or more types can be used in combination.

Although it is not particularly limited content of nonaqueous solvent carbonates, preferred properly 1 content of ethylene carbonate in the nonaqueous solvent total amount from 9.9 to 5 9.9 by weight ^_0/0, more preferably 2 5 It is 50% by weight, particularly preferably 25 to 45% by weight. If the content is significantly lower than 19.9% by weight, in the secondary battery containing the nonaqueous electrolyte of the present invention, there is a possibility that the reaction between the negative electrode and the nonaqueous electrolyte in a high-temperature environment may not be suppressed. If the content exceeds 59.9% by weight, problems such as easy solidification at low temperatures may occur.

The content of γ-butyrolactone in the non-aqueous solvent used together with the halogenated benzenes is not particularly limited, but is preferably 40 to 80% by weight, more preferably 50 to 80% by weight of the whole non-aqueous solvent. %, Particularly preferably 55 to 75% by weight.

In the present invention, one of the carbonates or y-butyrolataton can be used alone, but a combination of two or more carbonates or a combination of the carbonates and dibutyrolactone is preferred.

In particular, in the secondary battery containing the non-aqueous electrolyte of the present invention, from the viewpoint of improving the capacity retention during high-temperature storage, a combination of a cyclic carbonate and a chain carbonate, a combination of two or more cyclic carbonates Are preferred. From the viewpoint of suppressing gas generation during high-temperature storage, a combination of a cyclic carbonate and γ-butyrolatatone, a combination of two or more cyclic carbonates, and the like are preferable. From the viewpoint of improving safety, a combination of a cyclic carbonate and γ-petit mouth ratatone is preferable. Furthermore, from the viewpoint of compatibility between high-temperature storage characteristics and safety, a combination of ethylene carbonate and γ-butyrolatatone, a combination of ethylene carbonate and propylene carbonate, and a combination of ethylene carbonate and ethyl methyl carbonate Preferred are a combination of ethylene carbonate, ethynolemethine carbonate and ethynolecarbonate.

In the non-aqueous electrolyte of the present invention, the non-aqueous solvent contains an amination compound contained as an impurity. Zenzens are benzenes having an amino group as a substituent on a benzene ring. Although many such benzenes are known, benzenes having an amino group and one or more methyl groups as substituents on the benzene ring, such as aminated toluene and aminated xylene, are among them. It has been found by the inventors of the present invention that these types of batteries have a particularly bad effect on the safety of the secondary battery containing the nonaqueous electrolyte of the present invention during overcharge.

Both aminated toluene and aminated xylene are used as raw material compounds for halogenated benzenes, and do not react with halogenated toluene and xylene halide depending on the reaction conditions and the degree of purification. It is easy to remain as it is. Commercially available halogenated benzenes generally include aminated toluene and / or aminated xylene. For example, in o-fluorotoluene manufactured by Wako Pure Chemical Industries, 2-aminotoluene (auto / laizin) power of 1000 ppm remained.

Specific examples of aminated toluene include 2-aminotoluene, 3-aminotoluene, 4-aminotoluene, 2,3-diaminotoluene, 2,4-diaminotoluene, 2,5-diaminotoluene, and 2,6-aminotoluene. And diaminotoluene and 3.4-diaminotoluene.

Specific examples of aminated xylene include 2-amino-p-xylene, 2-amino-m: xylene, 3-amino-o-xylene, 4-amino_o-xylene, and 2,5-diamino-p. —Xylene and the like.

One or more of aminated toluene and aminated xylene may each be contained in a non-aqueous solvent. In addition, one or more aminated toluene and one or more aminated xylene may be simultaneously contained in the nonaqueous solvent.

The total content of the aminated benzenes in the non-aqueous solvent must be less than 100 ppm, more preferably 50 p or less. If the nonaqueous solvent contains 100 ppm or more, abnormal heat generation at the time of overcharging occurs more frequently in the secondary battery containing the nonaqueous electrolyte of the present invention, and the safety may be reduced. is there.

In order to make the content of the aminated benzenes in the non-aqueous solvent less than 100 ppm, for example, the halogenated benzenes may be highly purified. As a method for advanced purification, distillation purification can be applied to halogenated benzenes having a melting point of less than 50 ° C. At that time, it is preferable to use equipment having a distillation capacity of 5 or more distillation stages. For halogenated benzenes having a melting point of 50 ° C or higher, purification by crystallization can be applied.

The non-aqueous solvent in the non-aqueous electrolyte of the present invention contains halogenated benzenes as an essential component, and preferably contains carbonates or γ-butyrolataton together with the halogenated benzenes.

In the non-aqueous electrolyte of the present invention, a solvent other than the non-aqueous solvent can be used as an auxiliary component together with the non-aqueous solvent. As the auxiliary component, any of those used in non-aqueous electrolytes for secondary batteries can be used. For example, vinylene carbonate, bierethylene carbonate, phenylethylene carbonate, γ-valerolactone, methyl methyl pionate, propion Ethyl acid, ethyl acetate, acetonitrile, 2-methinofuran, furan, thiophene, teconocarbonate, ethylenesanolefite, 12-crown-14, tetraethyleneglycone reginomethinolate Examples include 3-propane sultone, sulfobenzoic anhydride, divinyl sulfone, 3-hydroxyl-l-propenesulfonic acid-gamma-sultone, and tris (trioctyl) phosphate.

Among such subcomponents, vinylene carbonate, 1,3-propanesultone, sulfobenzoic anhydride, divinylsulfone, 3-hydroxy-11-propenesulfonate-γ-sultone, etc. are the non-aqueous electrolytes of the present invention. In a secondary battery containing, a dense protective film is formed on the negative electrode surface, making it possible to further reduce the reactivity between the negative electrode and the nonaqueous electrolyte, and to improve the discharge characteristics during storage and the stability during high-temperature storage. It is preferable because it can be improved. As the accessory component, one type can be used alone, or two or more types can be used in combination.

Although the amount of the auxiliary component is not particularly limited, it is preferably based on the total weight of the nonaqueous solvent. It is desirable to select from the range of 10% by weight or less, more preferably 0.1% to 5% by weight, particularly preferably 0.1% to 3% by weight. If more than 10% by weight of the subcomponent is used, the ion permeability of the protective film on the negative electrode surface may be reduced, and the low-temperature discharge characteristics may be significantly impaired.

As the electrolyte to be dissolved in a non-aqueous solvent, it can be one commonly used in this field, for example, lithium perchlorate (L i C 10 _4), lithium hexafluorophosphate (L i PF _6), four lithium fluoride borate (L i BF _4), lithium hexafluoroarsenate _{(L i A s F 6)} , triflumizole Ruo b meth lithium sulfonate _{_{(L i CF 3 S0 3)}} , bis triflate Ruo b methylsulfonyl El Imi Dorichiumu (L i N (CF 3 S 0 2) 2), bi scan penta full O Roe chill sulfonyl Imi Dorichiumu _{(L i N (C 2 F} 5 S_〇 ₂₎ ₂₎ include lithium salts such as. One type of electrolyte can be used alone, or two or more types can be used in combination. In particular, when a mixed salt containing Li BF ₄ and Li PF ₆ is used, the cycle life at a high temperature of the secondary battery including the nonaqueous electrolyte of the present invention can be further improved.

The amount of the electrolyte dissolved in the non-aqueous solvent is not particularly limited and can be appropriately selected from a wide range, but is preferably in the range of 0.5 to 2.5 mol ZL, and more preferably in the range of 1 to 2.5 mol // L. It is desirable.

The non-aqueous electrolyte of the present invention is prepared, for example, by adding a carbonate or γ-petit mouth ratato to halogenated benzenes as necessary to prepare a non-aqueous solvent, and dissolving the electrolyte therein. Can be manufactured by The non-aqueous electrolyte can be in a desired form such as a liquid (non-aqueous electrolyte) or a gel.

Although the amount of the non-aqueous electrolyte used is not particularly limited, it is preferably 0.2 to 0.6 g, more preferably 0.25 to 0.55 g, per 1 O OmAh of the battery unit capacity.

(Non-aqueous electrolyte secondary battery)

A non-aqueous electrolyte secondary battery of the present invention includes a positive electrode, a negative electrode, and the non-aqueous electrolyte of the present invention.

That is, the non-aqueous electrolyte secondary battery of the present invention is a non-aqueous electrolyte of the present invention as a non-aqueous electrolyte. Except for the use of disintegration, the same structure as a conventionally known nonaqueous electrolyte battery can be adopted.

ADVANTAGE OF THE INVENTION According to the non-aqueous electrolyte secondary battery of this invention, when overcharged by the failure of the charger of the portable device in which this is built-in, etc., and the electric potential of a positive electrode rises, the shutdown by a separator is reliably produced. Therefore, the overcharge state can be safely terminated. In other words, in an overcharged state, an exothermic reaction is caused by the oxidation reaction of halogenated benzenes, so that the battery temperature can be quickly raised to the shutdown temperature of the separator. Can be. For this reason, the content of aminated benzenes is reduced to less than 100 ppm to perform a smooth oxidation reaction, thereby avoiding thermal runaway.

If the nonaqueous solvent contains more than 100 ppm of aminated benzene, the oxidation reaction starts to occur earlier than the halogenated benzene, so that the entire exothermic reaction is slower than the halogenated benzene compound alone. In such a situation, the battery temperature does not quickly rise to the separator shutdown temperature, the separator shutdown is incomplete, and the overcharge current cannot be completely cut off. If the air continues to flow, there is a risk of thermal runaway.

Hereinafter, the nonaqueous electrolyte secondary battery of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view schematically showing a configuration of a nonaqueous electrolyte secondary battery 1 according to a first embodiment of the present invention. FIG. 2 is a partial cross-sectional view as viewed from the section line II-II shown in FIG.

The nonaqueous electrolyte secondary battery 1 includes a container body 2 formed in a rectangular cup shape, an electrode group 3 housed in the container body 2, a lid plate 4 for sealing the container body 2, and a container body 2 A positive electrode tab 5 inserted between the electrode plate 3 and the positive electrode 10 in the electrode group 3, and a negative electrode 1 inserted between the container body 2 and the lid plate 4 and connected to the positive electrode 10 in the electrode group 3. And a negative electrode tap 6 connected to 1.

The container body 2 is formed of a laminate film including an outer protective layer 7, an inner protective layer 8, and a metal layer 9 disposed between the outer protective layer 7 and the inner protective layer 8. The outer protective layer 7 and the inner protective layer 8 are resin films mainly composed of a thermoplastic resin, preferably a heat-resistant thermoplastic resin. Specific examples of the thermoplastic resin include, for example, polyethylene, polypropylene, polyolefin such as cyclic polyolefin, polyamide, polyester, crystalline polyester, high-density polyethylene, low-density polyethylene, linear low-density polyethylene, and ethylene-vinyl acetate. Copolymers, polyacryloetrile, polyvinylidene chloride, and the like. Resin film

It may be a laminate of resin films containing two or more different thermoplastic resins. Examples of the metal constituting the metal layer 9 include metals such as aluminum, stainless steel, iron, copper, nickel, titanium, molybdenum, and gold, and metal oxides such as silicon oxide and aluminum oxide. Although the thickness of the laminate film can be appropriately selected from a wide range, it is preferably 50 to 300 / m. The edge 2a of the container body 2 is wide, and the container body 2 and the cover plate 4 are bonded by the edge 2a.

Electrode group 3 is formed by combining positive electrode 10, negative electrode 11 and separator 12. Specifically, the electrode group 3 has a structure in which a laminate including the positive electrode 10, the negative electrode 11, and the separator 12 disposed between the positive electrode 10 and the negative electrode 11 is wound into a flat shape. Formed in

The positive electrode 10 includes a current collector, and a positive electrode layer supported on one or both surfaces of the current collector and containing an active material.

As the current collector, those commonly used in this field can be used, and examples thereof include a conductive substrate. Examples of the metal forming the conductive substrate include aluminum, stainless steel, nickel, and the like. The conductive substrate may have a porous structure or a non-porous structure.

The positive electrode layer contains a positive electrode active material, a conductive agent, and a binder.

As the positive electrode active material, those commonly used in this field can be used, such as manganese dioxide, lithium manganese composite oxide, lithium-containing nickel oxide, lithium-containing cobalt oxide, lithium-containing nickel-cobalt oxide, and lithium-containing iron. Oxides, metal oxides such as vanadium oxides containing lithium, titanium disulfide, Chalcogen compounds such as molybdenum sulfide; Among them, lithium-containing organic cobalt oxide (e.g. L i C o O _2), lithium-containing nickel cobalt oxides (e.g. _{_{L i N i 8 C o 0}} . 2 O 2), Richiumuma, manganese composite oxide (for example if It is preferable to use L i M n ₂ 〇 ₄ and L i M n 0 ₂ ) because a high voltage can be obtained. One kind of the positive electrode active material can be used alone, or two or more kinds can be used in combination.

As the conductive agent, those commonly used in this field can be used, and examples thereof include acetylene black, carbon black, and graphite. One kind of the conductive agent can be used alone, or two or more kinds can be used in combination as needed.

As the binder, those commonly used in this field can be used, and examples thereof include polytetrafluoroethylene, polyvinylidene fluoride, polyethersulfone, ethylene-propylene-one-gen copolymer, and styrene-butadiene rubber. One kind of binder can be used alone, or two or more kinds can be used in combination as needed.

The mixing ratio of the positive electrode active material, the conductive agent and the binder is preferably in the range of 80 to 95% by weight of the positive electrode active material, 3 to 20% by weight of the conductive agent, and 2 to 7% by weight of the binder. .

The positive electrode 10 is produced, for example, by suspending a positive electrode active material, a conductive agent, and a binder in a suitable solvent, applying the suspension to a current collector, and drying to form a thin plate. The negative electrode 11 includes a current collector and a negative electrode layer supported on one or both surfaces of the current collector.

As the current collector, those commonly used in this field can be used, and examples thereof include a conductive substrate. Examples of the metal constituting the conductive substrate include copper, stainless steel, nickel, and the like. The conductive substrate may have a porous structure or a non-porous structure.

The negative electrode layer contains a negative electrode active material and a binder.

As the negative electrode active material, a material that absorbs and releases lithium ions can be used, for example, a graphite material or a carbonaceous material such as graphite, coatas, carbon fiber, spherical carbon, pyrolytic gas-phase carbonaceous material, and resin fired body. , Thermosetting resin, isotropic pitch, mesophase pitch-based carbon, mesophase pitch-based carbon fiber, mesophase spheroids, etc. (Especially, mesophase pitch-based carbon fiber has higher capacity / charge-discharge cycle characteristics. (Preferably) by heating at 500 to 300 ° C., or a graphite material, a carbonaceous material, or a lucogen compound such as titanium disulfide, molybdenum disulfide, or niobium selenide, aluminum, or aluminum. Light metals such as alloys, magnesium alloys, lithium and lithium alloys or alloys thereof. Among them,

It is desirable to use a graphitic material containing graphite crystals having a (002) plane spacing d002 of preferably 0.34 nm or less, more preferably 0.33711 m or less. A non-aqueous electrolyte secondary battery provided with a negative electrode containing such a graphite material as a negative electrode active material has significantly improved battery capacity and large current discharge characteristics. As the negative electrode active material, one type can be used alone, or two or more types can be used in combination.

As the binder, those commonly used in this field can be used, and examples thereof include polytetraphenylene ethylene, polyvinylidene fluoride, ethylene-propylene-one-gen copolymer, styrene-butadiene rubber, and carboxymethinoresenolerose. You. One type of binder can be used alone, or two or more types can be used in combination.

The compounding ratio of the negative electrode active material and the binder is preferably in the range of 80 to 98% by weight of the carbonaceous material and 2 to 20% by weight of the binder.

The negative electrode 11 is prepared, for example, by mixing a negative electrode active material and a binder in the presence of an appropriate solvent, applying the obtained suspension to a current collector, drying the resultant, and then pressing once at a desired pressure. Or it is produced by multi-stage pressing 2 to 5 times.

As the separator 12, those commonly used in this field can be used, and examples thereof include a microporous membrane, a woven fabric, and a nonwoven fabric, and a laminate of the same material or different materials among them. Above all, when the temperature of the electrode group 3 rises abnormally due to heat generation due to overcharging or the like, the microporous membrane plastically deforms the constituent resin and closes the fine pores. This is preferable because it shuts off, prevents further heat generation, and can safely end the overcharged state. Examples of the material forming the separator 12 include polyethylene, polypropylene, an ethylene-propylene copolymer, and an ethylenebutene copolymer. These materials can be used alone or in combination of two or more.

Electrode group 3 includes, for example, (1) a positive electrode 10 and a negative electrode 11 (1) Positive electrode (10) and negative electrode (11) are spirally wound with separator (12) between them, and then compressed radially Or (3) the force of bending the positive electrode 10 and the negative electrode 11 one or more times with the separator 12 interposed therebetween, or (4) the force between the positive electrode 10 and the negative electrode 11 with the separator 12 interposed therebetween. It is produced by a lamination method.

The electrode group 3 need not be pressed, but may be pressed to increase the integrated strength of the positive electrode 10, the negative electrode 11, and the separator 12. It is also possible to perform heating during pressing.

Electrode group 3 can contain an adhesive polymer compound in order to increase the integration strength of positive electrode 10, negative electrode 11 and separator 12. The adhesive polymer compound is preferably one that can maintain high adhesiveness while holding the non-aqueous electrolyte, and more preferably has high lithium ion conductivity. Specific examples include polyacrylonitrile, polyatalylate, polyvinylidene fluoride, polyvinyl chloride, and polyethylene oxide.

Electrode group 3 is impregnated with the non-aqueous electrolyte of the present invention and held.

The cover plate 4 is formed of a laminate film including an outer protective layer 7, an inner protective layer 8, and a metal layer 9 disposed between the outer protective layer 7 and the inner protective layer 8. The same laminating film as the laminating film of the container body 2 can be used as the laminating film.

One end of the positive electrode tab 5 is connected to the positive electrode 10, passes between the container body 2 and the cover plate 4, and the other end 5 a is drawn out of the container body 2, and functions as a positive electrode terminal. Materials commonly used in this field can be used as the material constituting the positive electrode tab 5, and examples thereof include aluminum, nickel, and titanium.

One end of the negative electrode tab 6 is connected to the negative electrode 11, passes between the container body 2 and the cover plate 4, and the other end 6 a is drawn out of the container body 2, and functions as a negative electrode terminal. As the material constituting the negative electrode tab 6, those commonly used in this field can be used, and examples thereof include copper, nickel, and a laminate in which a nickel layer is formed on a copper foil by plating or the like. The nonaqueous electrolyte secondary battery 1 can be manufactured in the same manner as the conventional battery manufacturing method. For example, the positive electrode tab 5 and the negative electrode tab 6 are connected to the electrode group 3, and the electrode group 3 is mounted in the container body 2 so that a part of each of the positive electrode tab 5 and the negative electrode tab 6 is outside the container body 2. Place. Further, the cover plate 4 and the container body 2 are overlapped so that the inner protective layer 8 of the cover plate 4 and the inner protective layer 8 of the edge 2a of the container body 2 are in contact with each other, and the portion is bonded by heat sealing or the like. By immobilization, the electrode group 3 is hermetically sealed in the container body 2, and the nonaqueous electrolyte battery 1 is obtained.

It should be noted that the non-electrolyte secondary battery of the present invention is not limited to the form of the non-electrolyte battery 1, but may be various forms of batteries such as a cylindrical form, a square form, and a coin form. .

The non-aqueous electrolyte secondary battery of the present invention can be used for the same applications as those to which a non-aqueous electrolyte secondary battery is conventionally applied. Examples include various electronic devices, especially mobile electronic devices, such as mobile communication devices such as mobile phones and mopiles, portable personal computers such as notebook personal computers and palmtop personal computers, and the like. It can be suitably used as a power source for cameras, digital cameras, integrated video cameras, portable CD (MD) players, etc.

【Example】

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

(Example 1)

Lithium cobalt oxide _{_{(L i x C o O 2}} ; however, X is 0 rather X 1) to 9 0 parts by weight powder powder, acetylene black 5 parts by weight, dimethylformamidine de polyvinylidene fluoride 5 parts by weight The solution was added and mixed to prepare a slurry. This slurry is applied to both sides of a 15 μππ thick aluminum foil (positive electrode current collector), dried, and pressed to carry a 60 / im thick positive electrode layer on both sides of the current collector. A positive electrode having the structure described above was produced.

Mesophase pitch-based carbon fiber heat-treated at 300 ° C as a carbonaceous material (powder 95 parts by weight of a powder having a (002) plane spacing (d 00 2) of 0.336 η m) determined by X-ray diffraction and 5 parts by weight of polyvinylidene fluoride in dimethylformamide solution Was mixed to prepare a slurry. This slurry was applied to both sides of a copper foil (negative electrode current collector) having a thickness of 12 μπι, dried, and pressed to form a negative electrode having a structure in which a negative electrode layer having a thickness of about 12 μπι was supported on both surfaces of the current collector. Produced.

The plane distance d002 of the (002) plane of the carbonaceous material was determined from the powder X-ray diffraction spectrum by the half-width width midpoint method. At this time, scattering correction such as Lorentz scattering was not performed.

A microporous polyethylene membrane having a thickness of 25 ιη and a porosity of 45% was used.

Preparation of electrode group

A positive electrode lead made of strip-shaped aluminum foil (thickness: 100 zm) was ultrasonically welded to the positive electrode current collector, and a negative electrode lead made of strip-shaped nickel foil (thickness: 100 / im) was ultrasonically welded to the negative electrode current collector. Thereafter, the positive electrode and the negative electrode were spirally wound therebetween with a separator interposed therebetween to prepare an electrode group. The electrode group was pressed into a flat shape by heating with a press machine.

Ethylene carbonate (EC), γ-butyrolataton (GBL), ο-chlorotoluene (ο-CT; oxidation potential with respect to lithium metal 4.8 V) and tris (trioctyl) phosphate are weight ratio (EC : GBL: o-CT: TOP) was adjusted to 35: 59.5: 5: 0.5 to prepare a non-aqueous solvent. Lithium tetrafluoroborate (L i BF ₄ ) was dissolved in the obtained non-aqueous solvent so as to have a concentration of 1.5 mol ZL to prepare a non-aqueous electrolyte solution of the present invention. From the results of gas chromatography analysis, the non-aqueous solvent contained 2-aminotoluene as an aminated benzene, and the content was 30 ppm or less.

A 100 / Zm-thick laminating film in which both sides of aluminum foil are covered with polyethylene is formed into a rectangular cup shape by a press machine, and the electrode group is placed in the obtained container. Stowed.

Next, moisture contained in the electrode group and the laminate film was removed by subjecting the electrode group in the container to vacuum drying at 80 ° C. for 12 hours.

After injecting the non-aqueous electrolyte into the electrode group in the container so that the amount per 1 Ah of battery capacity becomes 4.8 g, the same laminated film as above is placed on the upper surface of the container and sealed by heat sealing. A non-aqueous electrolyte secondary battery having the structure shown in FIGS. 1 and 2 and having a thickness of 3.6 mm, a width of 35 mm, a height of 62 mm, and a nominal capacity of 0.65 Ah was assembled.

The non-aqueous electrolyte secondary battery was subjected to constant current and constant voltage charging to 4.2 V at 0.2 C at room temperature for 15 hours as an initial charge / discharge process, and then to 3 V at room temperature at 0.2 C. 0 V to produce a nonaqueous electrolyte secondary battery.

Here, 1 C is the current required to discharge the nominal capacity (Ah) in one hour. Therefore, 0.2 C is the current value required to discharge the nominal capacity (Ah) in 5 hours.

(Examples 2 to 22)

A non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 1, except that the composition of the non-aqueous solvent and the content of the aminated benzenes were changed as shown in Table 1.

In Table 1, o_FT is o-fluorotoluene (oxidation potential with respect to lithium metal 4.9 V), p-CT is p-chlorotoluene (oxidation potential with respect to lithium metal 4.8 V) ), 2 FPX is 2-fluoro-] p-xylene (oxidation potential with respect to lithium metal 4.7 V).

In Table 1, TOP of the minor component is tris (trioctyl) phosphate, VC is vinylene carbonate,? 3 indicates 1,3-propane sultone, SBAH indicates sulfobenzoic anhydride, DVSU indicates divinylsulfone, and PRS indicates 3-hydroxy-1-1-pentopensurenoleic acid-γ-snorethone.

In Table 1, 2-AT of aminated benzene indicates 2-aminotoluene and 2-APX indicates 2-amino-p-xylene.

(Comparative example:! ~ 1 1)

Change the composition of the non-aqueous solvent and the content of aminated benzenes as shown in Table 1. A non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 1 except for the above.

(Test Example 1)

An overcharge test was performed on each of the 10 nonaqueous electrolyte secondary batteries obtained in Examples 1 to 22 and Comparative Examples 1 to 11. The overcharge test is to record the number of non-aqueous electrolyte secondary batteries that continue to charge at a current value of 2 C and generate abnormal heat or fire. Table 1 shows the ratio (abnormal heat generation rate,%) of the total number of batteries that generated abnormal heat or ignition.

【table 1】

Used in As is evident from Table 1, the secondary batteries of Examples 1-22 using a non-aqueous solvent containing halogenated benzenes and containing less than 100 ppm of aminated benzenes are as follows. Of the 10 batteries that underwent the overcharge test, few generated abnormal heat, and at most two batteries (20% or less) had a large effect of safely terminating the overcharged state. In particular, the content of aminated benzenes is 50 ppm or less. One CT, p - secondary battery CT _N o-Examples 1 to 4 FT was added, the content of the amination benzenes as compared with the secondary batteries of Example 5 9 0 ppm, further overcharge The effect of safely terminating the state is great.

On the other hand, the non-aqueous electrolyte secondary batteries of Comparative Examples 1 to 11 using halogenated benzenes and containing nonaqueous solvents having an aminated benzene content of 100 ppm or more were all 1 ° C. Three or more of the individuals developed abnormal fever.

The present invention may be embodied in various other forms without departing from its spirit or essential characteristics. Therefore, the above-described embodiment is merely an example in every respect, and the scope of the present invention is set forth in the appended claims, and is not limited by the specification. Further, all modifications and changes belonging to the claims are within the scope of the present invention.

[Industrial applicability]

INDUSTRIAL APPLICABILITY The nonaqueous electrolyte and the nonaqueous electrolyte secondary battery of the present invention have a remarkably low rate of abnormal heat generation during overcharge and have extremely high safety.

It can be used as a safe power supply for electronic devices such as mobile communication devices, notebook computers, palmtop computers, integrated video cameras, portable CD (MD) players, and cordless phones.

Claims

The scope of the claims

1, in a non-aqueous electrolyte containing a non-aqueous solvent and an electrolyte,

A non-aqueous electrolyte characterized in that the non-aqueous solvent contains halogenated benzenes and the content of aminated benzenes contained as impurities in the non-aqueous solvent is less than 100 ppm.

2. The non-aqueous electrolyte according to claim 1, wherein the non-aqueous solvent contains, in addition to the halogenated benzenes, carbonates and lactones.

3. The method according to claim 1, wherein the halogenated benzene is at least one selected from halogenated toluene and halogenated xylene having one or more chlorine atoms or fluorine atoms. Non-aqueous electrolyte.

4. Norogeni-dani benzenes include ο-chlorotonolene, ρ-chlorotonolene and others. The non-aqueous electrolyte according to any one of claims 1 to 3, wherein the non-aqueous electrolyte is at least one selected from one fluorotoluene.

5. The non-aqueous electrolyte according to any one of claims 1 to 4, wherein the aminated benzene is at least one selected from aminated toluene and aminated xylene.

6. The nonaqueous electrolyte according to any one of claims 1 to 5, wherein the aminated benzene is at least one selected from 2-aminotoluene, 4-aminotoluene and aminoxylene.

7. A non-aqueous electrolyte secondary battery comprising: a positive electrode; a negative electrode; and the non-aqueous electrolyte according to any one of claims 1 to 6.